It’s well known that a mother’s actions during pregnancy can affect the health of her developing fetus. But for the first time, researchers have shown that, in mice,the offspring of physically active expectant mothers are more active than those born to more lethargic moms-to-be.

Advertisement

In the new study, researchers from Baylor College of Medicine selected a group of adult female mice that ran an average of six miles every day on running wheels, and then kept track of their physical activity leading up to and throughout their pregnancies. After the runners were selected, half the mice’s running wheels were locked in place, while the other half had functional wheels in their cages. Once the mothers gave birth, a team of undergraduate researchers from Rice University — Jesse Eclarinal and Shaoyu Zhu — closely monitored the offspring, measuring their weight, eating habits, and physical activity around the onset of weaning, adolescence, and adulthood.

Advertisement

Advertisement

When the offspring of exercising mothers — who continued to slowly run up to a mile a day into their third trimesters — had access to wheels, they were more physically active than the litters of less active mothers.

“These findings may give women some additional motivation to get some physical activity.”

“I’ve been studying developmental programming models for about 15 years now, and this is the biggest effect that we’ve ever seen,” says Robert Waterland, an associate professor at Baylor and principle author on the study. The effect appeared in female offspring around the time they reached sexual maturity — at 60 days old — but appeared later and to a lesser extent in male offspring.

The litters of both active and sedentary mothers had similar body weights and compositions, but when the researchers gave the female offspring access to running wheels for three straight weeks when they were 300 days old, the litters of active mothers lost more fat than the controls.

So what does this mean for most of us?

“I believe this effect is likely to be true in humans as well,” Waterland says. Brain development in humans and mice is guided by sensory inputs; the visual cortex, for example, only flourishes if the brain receives signals from the eyes. Waterland believes the system that regulates physical activity levels may also be guided by sensory input during development — in this case, fetal movement as a mother walks or runs.

More research is necessary to test out his theory, but the new findings are not inconsistent with human studies so far. Severalstudies have found a correlation between moms’ exercise routines during pregnancy and children’s physical activity levels, but it’s still unclear if that relationship is due to developmental influences or just parents setting good examples. Waterland plans to carry out human studies in the future to find out, but in the meantime, it can’t hurt for expectant mothers to take these new findings to heart.

“Pregnant women are already recommended to engage in moderate physical activity,” Waterland says. “These findings may just give women some additional motivation to get up and get some healthy physical activity during pregnancy.”